Study: 1,700 Americans could catch swine flu

April 29, 2009

As people around the world anxiously refresh Internet maps showing new locations of suspected swine flu infections, a Northwestern University professor has already mapped out the worst case scenario for the outbreak.

In four weeks, around 1,700 Americans could be infected with the disease, according to a model programmed by Dirk Brockmann, associate professor of engineering sciences and applied mathematics at Northwestern. About 100 of those cases would be in Chicago, Brockmann said.

But Brockmann said his model, based on direct and indirect measures of human mobility, predicts the spread of the disease as if no interventions are put in place to slow its spread.

Given the worldwide attention on the disease by public health organizations such as the Centers for Disease Control and Prevention and the World Health Organization, he would expect actual numbers to be much lower.

Even the worst case scenario of 1,700 infections is a relatively low number given the media attention, Brockmann said, though he understands the growing fear.

"When people get this information, they immediately see themselves as one of the 1,700, not part of the other 299 million," Brockmann said.

Brockmann began creating computer models of pandemics in 2004 after the SARS scare in China, using data on air travel and the movement of dollar bills as measures of how humans move around the world and potentially carry disease. The models present a new analogy of how disease travels in our interconnected world, Brockmann said.

"If everyone traveled like they did in the 14th century, everything would spread like forest fires," Brockmann said. "But when modern travel is involved, the spatial-temporal pattern is much more complex. It's sort of like exploding stars."

Thus travel hubs like New York, Miami and Chicago should see the first cases of the disease, and Brockmann said he was not surprised to hear about the first suspected case in Chicago this morning. He reserved his surprise for the fact that his model agreed with a separate model from Indiana University researchers predicting the spread using completely different data.

"We were very happy that the modeling approach works," Brockmann said. "Of course in this context, saying we're very happy is weird."